There are two plans in MuxEmail.
Free Plan (all the features available with an upper limit of 5,000 subscribers)
Unlimited Plan at $19/month (5,000 to infinity)
Since MuxEmail connects with your Amazon SES account to send emails, you might also need to pay Amazon SES depending on the number of emails you send.
So the first 62,000 emails you send every month is FREE on Amazon SES. After that they charge you $1 for every 10,000 emails sent.
So let's assume you have 20,000 subscribers and you send them emails 4 times a month. So you'll be paying MuxEmail $19 for the Unlimited Plan and around $1.8 to Amazon, costing you to just $20.8 to send out 80,000 emails to your 20,000 subscribers per month.
You can take a look at the image below to get an accurate idea of how much more money you would be saving by simply making the shift from your Email Service Provider to MuxEmail.